Biochemically active substances, such as enzymes, co-enzymes, enzyme inhibitors, hormones, antigens, antibodies, proteins, DNA, RNA etc., fixed on carriers such as cellulose, agarose, synthetic polymers, etc., are used in the separation, purification and transformation of other biochemically active substances. Properties required in such carriers include the following: (1) The carrier should be able to readily fix or immobilize a large quantity of a given biochemically active substance per unit weight of carrier; (2) The carrier should be biocompatible and sterilizable; (3) The carrier should have sufficient mechanical strength and stability so as to be capable of recycling many times with minimal loss of binding capacity; (4) The activity of the biochemically active substance while attached to the carrier should be good; (5) The materials which are held or entrapped by the biochemically active substance during use should be easily removable in order to permit ready availability of the biochemically active substance for re-use; and (6) The carrier, while possessing the foregoing properties, should be in a form which permits high flow rate of the fluids to be treated at low pressure drop. In the case of conventional carriers used to immobilize biochemically active substances, the aforementioned requirements are not adequately satisfied.
Polyimides have found extensive use in the electronics arena where they have proven useful in forming dielectric films as protective coatings on electronic and electrical devices, i.e. semiconductors, high temperature solder masks and bonding multilayer circuits. It is known in the polymer art to make all-aromatic polyimides by the condensation polymerization of dianhydrides and diamines to form polyamic acids which are then dehydrated to the polyimides (Edwards U.S. Pat. No. 3,179,634). Fryd U.S. Pat. No. 4,588,804 discloses polyimide compositions soluble in aprotic solvents. Gesslaer DE patent 3,523,615 discloses the use of polyimide coated materials, the surface of which are coated with gamma globulin. Wynberg WO patent 86/03840 discloses the use of polyimides (made from pyromellitic acid and bis(4-aminophenyl) oxide as immunoreagent carriers in thermochemiluminescence immunoassays.